Dynamic scheduling method for guaranteeing quality of service depending on network transmission traffic in large-scale IOT environment and system using the same

ABSTRACT

Disclosed herein are a dynamic scheduling method for guaranteeing Quality of Service QoS depending on network transmission traffic and a system using the same. The dynamic scheduling method includes assigning communication channels to respective nodes based on Identifications (IDs) of parent nodes corresponding to the respective nodes, setting priorities for assignment of time slots to the respective nodes in each quarter based on data traffic volumes corresponding to the respective nodes, and assigning time slots to the respective nodes in each quarter depending on the set priorities for assignment of the time slots.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2017-0094116, filed Jul. 25, 2017, which is hereby incorporated byreference in its entirety into this application.

BACKGROUND OF THE INVENTION 1. Technical Field

The present invention relates to a dynamic scheduling method forguaranteeing Quality of Service (QoS) depending on network transmissiontraffic in a large-scale Internet of Things (IoT) environment and to asystem using the dynamic scheduling method.

2. Description of the Related Art

Wireless sensor network technology for industrial Internet of Things(IoT) applications includes standards, such as Zigbee, an InternationalSociety of Automation (ISA) 100.11a standard, and a Wireless sensornetworking technology based on the Highway Addressable Remote Transducerprotocol (WirelessHART) standard, which define high-level communicationprotocols suitable for the requirements of related industries based onan Institute of Electrical and Electronics Engineers (IEEE) 802.15.4standard which is a Wireless Personal Area Network (WPAN) transmissionstandard.

The IEEE 802.15.4 standard, which is proposed for low-power, low-cost,and short-range wireless networks, has problems, such as a transmissiondelay, limitation in security of reliability, limited peer-to-peercommunication, and the absence of a low-power operation method suitablefor various qualities of service. Therefore, recently, in order to solveproblems with existing IEEE 802.15.4 technology in consideration ofrequirements of the International Telecommunication UnionRadiocommunication Sector (ITU-R) M.2002/M.2224 and to satisfy acommunication range of 1 km or more, reliable communication in a shadowarea, low-power implementation for a battery lifespan of 10 or moreyears, and minimum infrastructure technology requirements, a Weightlessv1.0 standard, IEEE 802 15.4e, g, k standards, etc. have been completelyestablished, and 15.4 m and 15.8 standards and the like are underdiscussion.

In the IEEE 802.15.4e standard, a Media Access Control (MAC) templatefor transmitting/receiving data using Time-Slotted Channel Hopping(TSCH) technology has been standardized. However, a schedulingalgorithm, which indicates the number of a time slot in which, and thenumber of a frequency channel through which, each node communicates witha parent node thereof in a periodically repeating cycle, is notpresented. Accordingly, the Internet Engineering Task Force (IETF) hasconducted research into TSCH-based communication scheduling through IPv6over the TSCH mode of IEEE 802.15.4e (6TiSCH) Working group since 2013,and is proposing a 6TiSCH Operation Sublayer (6top) protocol for two-wayscheduling negotiation in the form of a draft.

However, in order to satisfy various QoS requirements (e.g. transmissiondelay time, transmission success rate, duty cycle for low powerconsumption, etc.) of industrial IoT, a dynamic scheduling methoddepending on data traffic and network topology is needed. In connectionwith this, Korean Patent No. 10-1217813 discloses a technology relatedto “Method to determine priority of data transmission in wirelessnetwork”.

The above-described background technology is technological informationthat was possessed by the present applicant to devise the presentinvention or that was acquired by the present applicant during thecourse of devising the present invention, and thus such informationcannot be construed to be known technology that was open to the publicbefore the filing of the present invention.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a coloring-based dynamic distributed schedulingmethod and a system using the method, which can remove collisions andinterference when a large number of multi-hop nodes configured in alarge-scale IoT environment desire to transmit data to a root node, andcan satisfy various QoS requirements of industrial IoT.

Another object of the present invention is to provide a coloring-baseddynamic distributed scheduling method and a system using the method,which can satisfy various QoS requirements by dividing quartersaccording to the amount of network transmission traffic while avoidingcollisions and interference, occurring in transmission, and transmittingdata without overlapping by separating time and channels based oncoloring.

In accordance with an aspect of the present invention to accomplish theabove objects, there is provided a dynamic scheduling method forguaranteeing Quality of Service (QoS) depending on network transmissiontraffic, including assigning communication channels to respective nodesbased on Identifications (IDs) of parent nodes corresponding to therespective nodes; setting priorities for assignment of time slots to therespective nodes in each quarter based on data traffic volumescorresponding to the respective nodes; and assigning time slots to therespective nodes in each quarter depending on the set priorities forassignment of the time slots.

Assigning the time slots may be configured to assign the time slots suchthat a collision between neighboring communication channels does notoccur by applying graph coloring to the communication channels.

Assigning the time slots may be configured to sequentially determine,for a target node, whether a communication collision with the targetnode occurs in multiple time slots from a first time slot in a targetquarter, and to assign an earliest time slot in which a collision doesnot occur to the target node.

The dynamic scheduling method may further include when two or moretarget nodes interfere with each other using an identical channel in anidentical time slot in an identical target quarter, changing andassigning one or more of communication channels and time slots that areassigned to the interfering target nodes.

The target quarter may include one or more spare time slots for avoidinginterference, and changing and assigning the one or more of thecommunication channels and the time slots may be configured to assigndifferent time slots to the interfering target nodes using the sparetime slots.

Changing and assigning the one or more of the communication channels andthe time slots may be configured to, when two or more target nodesinterfere with each other using an identical channel in an identicaltime slot in an identical target quarter, assign different communicationchannels to the interfering target nodes.

Changing and assigning the one or more of the communication channels andthe time slots may be configured to, when the different communicationchannels are assigned to the interfering target nodes, assign differentcommunication channels to the interfering target nodes usingcommunication channels other than existing communication channels of theinterfering target nodes and existing communication channels of parentnodes of the interfering target nodes.

The dynamic scheduling method may further include assigningcommunication channels to respective nodes so as to receive an EnhancedBeacon (EB) message in a quarter EB interval, separate from existingquarters in which data is transmitted; allowing each of the nodes toreceive an EB message from a parent node corresponding thereto; and wheninformation, indicating that there is data to be transmitted in aquarter Broadcast (BR) interval, is included in the EB message,receiving broadcast data corresponding to the data to be transmitted inthe quarter BR interval.

Setting the priorities for assignment of time slots may be configured toset a priority for assignment of time slots to a higher level as a datatraffic volume corresponding to each node is larger.

Assigning the time slots may be configured to assign the time slots suchthat each node performs transmission once or less in each quarter.

In accordance with another aspect of the present invention to accomplishthe above objects, there is provided a system using a dynamic schedulingmethod for guaranteeing Quality of Service (QoS) depending on networktransmission traffic, wherein the dynamic scheduling method isconfigured to assigning communication channels to respective nodes basedon Identifications (IDs) of parent nodes corresponding to the respectivenodes, setting priorities for assignment of time slots to the respectivenodes in each quarter based on data traffic volumes corresponding to therespective nodes, and assigning time slots to the respective nodes ineach quarter depending on the set priorities for assignment of the timeslots.

The time slots may be assigned such that a collision between neighboringcommunication channels does not occur by applying graph coloring to thecommunication channels.

The time slots may be assigned by sequentially determining, for a targetnode, whether a communication collision with the target node occurs inmultiple time slots from a first time slot in a target quarter, and byassigning an earliest time slot in which a collision does not occur tothe target node.

The dynamic scheduling method may be configured to, when two or moretarget nodes interfere with each other using an identical channel in anidentical time slot in an identical target quarter, change and assignone or more of communication channels and time slots that are assignedto the interfering target nodes.

The target quarter may include one or more spare time slots for avoidinginterference, and the dynamic scheduling method may be configured toassign different time slots to the interfering target nodes using thespare time slots.

The dynamic scheduling method may be configured to, when two or moretarget nodes interfere with each other using an identical channel in anidentical time slot in an identical target quarter, assign differentcommunication channels to the interfering target nodes.

The dynamic scheduling method may be configured to, when the differentcommunication channels are assigned to the interfering target nodes,assign different communication channels to the interfering target nodesusing communication channels other than existing communication channelsof the interfering target nodes and existing communication channels ofparent nodes of the interfering target nodes.

The dynamic scheduling method may be configured to assign communicationchannels to respective nodes so as to receive an Enhanced Beacon (EB)message in a quarter EB interval, separate from existing quarters inwhich data is transmitted, allow each of the nodes to receive an EBmessage from a parent node corresponding thereto, and when information,indicating that there is data to be transmitted in a quarter Broadcast(BR) interval, is included in the EB message, receive broadcast datacorresponding to the data to be transmitted in the quarter BR interval.

The priorities for assignment of time slots may be set such that apriority for assignment of time slots is set to a higher level as a datatraffic volume corresponding to each node is larger.

The time slots may be assigned such that each node performs transmissiononce or less in each quarter.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a diagram illustrating a system using a dynamic schedulingmethod for guaranteeing Quality of Service (QoS) depending on networktransmission traffic according to an embodiment of the presentinvention;

FIG. 2 is a diagram illustrating an example in which the system using adynamic scheduling method for guaranteeing QoS depending on networktransmission traffic, illustrated in FIG. 1, assigns communicationchannels;

FIG. 3 is a diagram illustrating an example in which the system using adynamic scheduling method for guaranteeing QoS depending on networktransmission traffic, illustrated in FIG. 2, transmits pieces of data inrespective quarters;

FIG. 4 is a diagram illustrating an example in which the system using adynamic scheduling method for guaranteeing QoS depending on networktransmission traffic, illustrated in FIG. 3, assigns time slots inrespective quarters;

FIGS. 5 to 7 are diagrams illustrating a procedure for transmitting datadepending on the schedule illustrated in FIG. 4;

FIGS. 8 and 9 are diagrams illustrating a system using a dynamicscheduling method for guaranteeing QoS depending on network transmissiontraffic according to another embodiment of the present invention and adata transmission schedule based on the system;

FIG. 10 is a diagram illustrating an example in which the system using adynamic scheduling method for guaranteeing QoS depending on networktransmission traffic, illustrated in FIGS. 8 and 9, avoids interferenceand performs scheduling;

FIG. 11 is a diagram illustrating another example in which the systemusing a dynamic scheduling method for guaranteeing QoS depending onnetwork transmission traffic, illustrated in FIGS. 8 and 9, avoidsinterference and performs scheduling;

FIG. 12 is a diagram illustrating a method in which the system using adynamic scheduling method for guaranteeing QoS depending on networktransmission traffic, illustrated in FIG. 1, sends an Enhanced Beacon(EB) message and Broadcast (BR) data;

FIG. 13 is an operation flowchart illustrating a dynamic schedulingmethod for guaranteeing QoS depending on network transmission trafficaccording to an embodiment of the present invention; and

FIG. 14 is an operation flowchart illustrating an example of the timeslot assignment step illustrated in FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention may be variously changed, and may have variousembodiments, and specific embodiments will be described in detail belowwith reference to the attached drawings. The advantages and features ofthe present invention and methods for achieving them will be moreclearly understood from the following detailed description taken inconjunction with the accompanying drawings. Repeated descriptions anddescriptions of known functions and configurations which have beendeemed to make the gist of the present invention unnecessarily obscurewill be omitted below. The embodiments of the present invention areintended to fully describe the present invention to a person havingordinary knowledge in the art to which the present invention pertains.Accordingly, the shapes, sizes, etc. of components in the drawings maybe exaggerated to make the description clearer.

However, the present invention is not limited to the followingembodiments, but some or all of the following embodiments can beselectively combined and configured so that various modifications arepossible. In the following embodiments, terms such as “first” and“second” are not intended to restrict the meanings of components, andare merely intended to distinguish one component from other components.A singular expression includes a plural expression unless a descriptionto the contrary is specifically pointed out in context. In the presentspecification, it should be understood that terms such as “include” or“have” are merely intended to indicate that features or componentsdescribed in the present specification are present, and are not intendedto exclude the possibility that one or more other features or componentswill be present or added.

Embodiments of the present invention will be described in detail withreference to the accompanying drawings. In the following description ofthe present invention, the same reference numerals are used to designatethe same or similar elements throughout the drawings, and repeateddescriptions of the same components will be omitted.

FIG. 1 is a diagram illustrating a system 1 using a dynamic schedulingmethod for guaranteeing Quality of Service (QoS) depending on networktransmission traffic according to an embodiment of the presentinvention.

Referring to FIG. 1, the system 1 using a dynamic scheduling method forguaranteeing QoS depending on network transmission traffic according tothe embodiment of the present invention has a tree-structured routingpath in which communication devices 102 to 109, which use the dynamicscheduling method for guaranteeing QoS depending on network transmissiontraffic in an IEEE 802.15.4-based network, transmit data to a root node(top-level node) 101. Here, the process in which respective nodestransmit data to their parent nodes and the parent nodes transmit thedata to their parent nodes may be repeated, and thus the root node 101may finally receive all data.

However, when a large number of nodes configured in a large-scale IoTenvironment desire to simultaneously transmit data to the root node, aproblem may occur in operating a network for guaranteeing QoS due tocollisions or interference between the nodes.

Here, requirements for QoS may include a transmission delay time, atransmission success rate, a duty cycle for low power consumption, etc.

Here, the system 1 using a dynamic scheduling method for guaranteeingQoS depending on network transmission traffic avoids collisions andinterference that may occur in data transmission through datatransmission scheduling, in which time and channels are separated basedon coloring, in order to guarantee QoS in a large-scale IoT environment.

In detail, the system 1 using a dynamic scheduling method forguaranteeing QoS depending on network transmission traffic may assigntransmission channels based on receivers (parent nodes) (i.e.receiver-based channel assignment) to respective communication devices102 to 109, which use the dynamic scheduling method for guaranteeing QoSdepending on network transmission traffic, in order to diversifychannels, may establish quarters (regions) after the receiver-basedchannel assignment, may perform time slot coloring, may determinepriorities for time slot assignment based on the data traffic volumes ofrespective nodes, may assign time slots within each quarter depending onthe determined priorities for time slot assignment, and may transmitdata using the assigned time slots and transmission channels.

Here, the transmission channels of respective nodes may be assignedbased on the IDs of parent nodes corresponding thereto.

For example, when the ID of the parent node 101 is 1, the child nodes102 to 104 may assign transmission channels to ‘1’, which is the ID ofthe parent node 101.

Here, the data traffic volume of a specific node may mean the sum of theamount of data that is received from descendant nodes and is to betransmitted to the root node and the amount of data that is to betransmitted from the specific node to the root node.

For example, the data traffic volume of the node 102 may be ‘4’,obtained by summing a data volume of 3, which is transmitted from thenodes 105, 108, and 109, which are descendant nodes thereof, and a datavolume of 1 of the node 102 itself.

Here, the larger the data traffic volume, the higher the priority fortime slot assignment that may be set in each quarter.

In particular, the largest data traffic volume may be the total numberof quarters.

Here a time slot may be assigned once to each of the nodes within eachquarter.

Accordingly, each node may transfer data received from a descendant nodethereof to a parent node thereof once within each quarter, oralternatively, the node may transmit its own data to the parent nodewhen there is no data received from a descendant node, thus minimizing atransmission delay and sequentially transmitting data.

Also, since a minimum number of time slots are assigned and used totransmit and receive data, a duty cycle may be minimized, and thus powerconsumption may also be minimized.

FIG. 2 is a diagram illustrating an example in which the system 1 usinga dynamic scheduling method for guaranteeing QoS depending on networktransmission traffic, illustrated in FIG. 1, assigns communicationchannels.

Referring to FIG. 2, the system 1 using a dynamic scheduling method forguaranteeing QoS depending on network transmission traffic according tothe embodiment of the present invention has a tree-structured routingpath in which communication devices 102 to 109, which use the dynamicscheduling method for guaranteeing QoS depending on network transmissiontraffic in an IEEE 802.15.4-based network, transmit data to a root node101.

Here, node 9 109 has node 8 108 as a parent node, the node 8 108 hasnode 5 105 as a parent node, the node 5 105 has node 2 102 as a parentnode, and the node 2 102 has the node 1 (root node) 101 as a parentnode. Also, node 6 106 has node 3 103 as a parent node and the node 3103 has the root node 1 101 as a parent node. Further, node 7 107 hasnode 4 104 as a parent node and the node 4 104 has the root node 1 101as a parent node.

The ID of node M is M. For example, the ID of the node 1 is 1 and the IDof the node 2 is 2. The numeral in each node of FIG. 2 may mean the IDof the corresponding node.

When transmission channels are assigned to respective nodes 101 to 109,the transmission channels may be assigned based on the IDs of parentnodes thereof.

When a transmission channel is assigned to a corresponding one of thenodes 101 to 109, the transmission channel having a channel numberidentical to the ID of a parent node of the corresponding node may beassigned. When the ID of the parent node is equal to or greater than thetotal number of channels N, the transmission channel may be replacedwith a channel having a channel number corresponding to the remainderthat is obtained when the ID of the parent node is divided by N.

Here, referring to the IEEE 802.15.4 standard, the total number ofchannels is 16, and thus there may be channels from #0 to #15.

That is, the ID of the node 8 108, which is the parent node of the node9 109, is 8, and thus channel #8 may be assigned as the transmissionchannel 109 a of the node 9 109. Similarly, channel #5 may be assignedas the transmission channel 108 a of the node 8 108, channel #2 may beassigned as the transmission channel 105 a of the node 5 105, channel #1may be assigned as the transmission channel 102 a of the node 2 102,channel #3 may be assigned as the transmission channel 106 a of the node6 106, the channel #1 may be assigned as the transmission channel 103 aof the node 3 103, channel #4 may be assigned as the transmissionchannel 107 a of the node 7 107, and the channel #1 may be assigned asthe transmission channel 104 a of the node 4 104. Here, numeralsindicated on the left side of lines indicating transmission channelsbetween respective nodes of FIG. 2 may mean channel numbers of thecorresponding transmission channels.

Here, as the transmission channels 102 a to 104 a, the channel #1 isequally assigned to the node 2 102, the node 3 103, and the node 4 104.Therefore, in order to prevent collisions from occurring due to the useof the same transmission channel, there is a need to schedule datatransmission by assigning time slots.

FIG. 3 is a diagram illustrating an example in which the system 1 usinga dynamic scheduling method for guaranteeing QoS depending on networktransmission traffic, illustrated in FIG. 2, transmits pieces of data inrespective quarters.

Referring to FIG. 3, the system 1 using a dynamic scheduling method forguaranteeing QoS depending on network transmission traffic, illustratedin FIG. 2, assigns transmission channels based on the IDs of parentnodes to respective descendant nodes 102 to 109. However, since thenumber of channels is limited, there is a need to assign time slots ineach quarter so as to avoid collisions between channels.

Here, a node ID is indicated in each node of FIG. 3, and a data trafficvolume is indicated on the left side of the corresponding node, whereinthe data traffic volume is the sum of a data volume that is receivedfrom descendant nodes and is to be transmitted to the root node and adata volume that is to be transmitted from the corresponding node to theroot node.

That is, the data traffic volume of the node 2 102 is 4, the datatraffic volume of the node 5 105 is 3, the data traffic volumes of thenode 3 103, the node 4 104, and the node 8 108 are 2, and the datatraffic volumes of the node 6 106, the node 7 107, and the node 9 109are 1.

Here, in each quarter, the nodes 102 to 109 may transmit data once.

Further, the number of quarters may be the largest data traffic volume,among data traffic volumes corresponding to respective nodes.

That is, the data traffic volume of the node 2 102 is 4, which is thelargest data traffic volume, and thus the total number of quarters maybe 4.

Since all nodes perform data transmission once in each quarter, datavolumes to be transmitted by leaf nodes having a data volume other than0 may consequently be ‘0’. In order to simplify and represent thissituation, nodes having a data volume of 0 to be transmitted may beexcluded from illustration in the drawing.

For example, all nodes transmit data to parent nodes thereof once inquarter 1 (3 a), and thus the leaf nodes in the quarter 1, that is, thenode 6 106, the node 7 107, and the node 9 109, may have a data volumeof 0 to be transmitted in quarter 2. Further, after the quarter 1 haspassed, in the quarter 2, the node 2 102 may have a data traffic volumeof 3, the node 5 105 may have a data traffic volume of 2, and the node 3103, the node 4 104, and the node 8 108 may have a data traffic volumeof 1.

Further, all nodes transmit data to parent nodes thereof once in quarter2 (3 b), and thus the leaf nodes in the quarter 2, that is, the node 3103, the node 4 104, and the node 8 108, may have a data volume of 0 tobe transmitted in quarter 3. Also, after the quarter 2 has passed, inthe quarter 3, the node 2 102 may have a data traffic volume of 2, andthe node 5 105 may have a data traffic volume of 1.

Furthermore, all nodes transmit data to parent nodes thereof once in thequarter 3 (3 c), and thus a leaf node in the quarter 3, that is, thenode 5 105, may have a data traffic volume of 0 to be transmitted inquarter 4. Further, after the quarter 3 has passed, in the quarter 4,the node 2 102 may have a data traffic volume of 1.

Here, when graph coloring is applied to respective transmission channelsof the nodes, time slots may be separated using a total of three colors,and thus three time slots may be assigned in each quarter. Further, allnodes may transmit data using three time slots in each quarter.

FIG. 4 is a diagram illustrating an example in which the system 1 usinga dynamic scheduling method for guaranteeing QoS depending on networktransmission traffic, illustrated in FIG. 3, assigns time slots inrespective quarters.

Referring to FIG. 4, the system 1 using a dynamic scheduling method forguaranteeing QoS depending on network transmission traffic assigns timeslots so that data may be transmitted through quarter-based coloringwithout causing collisions or interference in each quarter.

In this case, the assignment of time slots may be performed using amethod such as that given in the following pseudo-code 1:

[Pseudo-code 1] repeat while(interference(u,t)==0 &&interference(parent(u),t)==0) t −> t+1 end while if(conflict(u)==0)schedule to send else if(t<quarter_bound) t −> t+1 else change thechannel t −> t+1until node (u) is scheduled

In the above pseudo-code 1, interference (u,t) indicates whetherinterference with a neighboring node occurs when node u transmits datain time slot t, parent (u) indicates a parent node of the node u,conflict (u) indicates whether a conflict (collision) in datatransmission/reception occurs when the node u transmits data, andquarter_bound indicates the maximum number of time slots assigned ineach quarter.

FIG. 4 illustrates scheduling realized such that nine time slots and sixchannels are distributed and assigned to a total of nine nodes in thesystem 1 using a dynamic scheduling method for guaranteeing QoSdepending on network transmission traffic, illustrated in FIG. 3, thusenabling data to be transmitted without causing collisions orinterference. In particular, in FIG. 4, data transmission is scheduledsuch that, in order to optimize scheduling, quarter 4 is omitted and alldata transmission tasks are terminated in quarter 3. Although dataaggregation is not described here, further optimized scheduling may beperformed if such data aggregation is used.

The larger the data traffic volume, the higher the priority for timeslot assignment that may be set in each quarter.

Here, when the priority for time slot assignment is set depending on thedata traffic volume, the priority that is assigned may become higher inthe sequence of the node 2, the node 5, the node 3, the node 4, the node8, the node 6, the node 7, and the node 9.

That is, channel #1 may be assigned to the node 2, and time slot #1 maybe assigned to the node 2 because there is neither a collision norinterference with other channels. Channel #2 is assigned to the node 5,but time slot #2 may be assigned to the node 5 due to the problem of acollision with the node 2. The channel #1 may be assigned to the node 3,and the time slot #2 may be assigned to the node 3 due to the problem ofa collision with the node 2. The channel #1 may be assigned to node 4,and time slot #3 may be assigned to the node 4 due to the problem of acollision with the node 2 and the node 3. Channel #5 may be assigned tothe node 8, and the time slot #1 may be assigned to the node 8 becausethere is no problem of a collision with other nodes. The channel #3 maybe assigned to the node 6, and the time slot #1 may be assigned to thenode 6 because there is no problem of a collision with other nodes.Channel #4 may be assigned to the node 7, and the time slot #1 may beassigned to the node 7 because there is no problem of a collision withother nodes. Channel #8 may be assigned to the node 9, and the time slot#2 may be assigned to the node 9 due to the problem of a collision withthe node 8.

In this way, since the time slots are assigned based on coloring, allnodes can transmit data using only a minimum number of time slots, andthus a transmission delay may be minimized.

FIGS. 5 to 7 are diagrams illustrating a procedure for transmitting datadepending on the schedule illustrated in FIG. 4.

The numeral in each node, illustrated in FIGS. 5 to 7, indicates the IDof the corresponding node, and the numeral on the left side of the nodeindicates the amount of data traffic to be transmitted from thecorresponding node. Also, among nodes from which the amount of datatraffic to be transmitted is ‘0’, leaf nodes may be omitted, and nodes,which are not omitted, may be indicated by dotted lines.

Referring to FIG. 5, in time slot 1, each of nodes 2 102 to 9 109 hasdata traffic of 1, and the node 2 102, the node 6 106, the node 7 107,and the node 8 108 transmit data to parent nodes thereof throughtransmission channels respectively assigned thereto depending on thetransmission schedule in the time slot 1.

After the time slot 1 has passed, the data traffic of each of the node 2102, the node 6 106, the node 7 107, and the node 8 108 becomes ‘0’.Among these nodes, the node 6 106 and the node 7 107 may be omittedbecause they are leaf nodes. Further, since the node 3 103, the node 4104, and the node 5 105 receive data from child nodes thereof, the datatraffic of each of the nodes 3, 4, and 5 becomes ‘2’.

Also, the node 3 103, the node 5 105, and the node 9 109 may transmitdata to parent nodes thereof through transmission channels respectivelyassigned thereto depending on the transmission schedule in the time slot2.

After the time slot 2 has passed, the data traffic of each of the node 3103 and the node 5 105 becomes ‘1’, and the data traffic of the node 9109 becomes ‘0’, and then the node 9 109 may be omitted. Also, the datatraffic of each of the node 2 102 and the node 8 108 becomes ‘1’.

Further, the node 4 104 transmits data to the parent node thereofthrough the transmission channel assigned thereto depending on thetransmission schedule in the time slot 3.

After the time slot 3 has passed, the data traffic of the node 4 104becomes ‘1’.

That is, when the time slot 1 to time slot 3 have passed in the quarter1, all nodes perform data transmission once, and the data traffic ofeach of the node 6 106, the node 7 107, and the node 9 109, which areleaf nodes in the quarter 1, becomes ‘0’. Furthermore, the data trafficof each of the node 2 to the node 5 and the node 8 (nodes 102 to 105 and108) becomes ‘1’.

Referring to FIG. 6, in time slot 4, each of the node 2 102 to node 5105 and the node 8 108 has data traffic of 1, and the node 2 102 and thenode 8 108 may transmit data to parent nodes thereof throughtransmission channels respectively assigned thereto depending on thetransmission schedule in the time slot 4.

After the time slot 4 has passed, the data traffic of each of the node 2102 and the node 8 108 becomes ‘0’. Of the nodes, the node 8 108 is aleaf node, and thus the node 8 may be omitted. Also, the node 5 105receives data from the child node thereof, and thus the data traffic ofthe node 5 105 becomes ‘2’.

Further, the node 3 103 and the node 5 105 transmit data to parent nodesthereof through transmission channels respectively assigned theretodepending on the transmission schedule in the time slot 5.

After the time slot 5 has passed, each of the node 2 102 and the node 5105 has data traffic of ‘1’. Also, the node 3 103 has data traffic of‘0’, and may be omitted because the node 3 103 is a leaf node.

Next, the node 4 104 transmits data to the parent node thereof through atransmission channel assigned thereto depending on the transmissionschedule in time slot 6.

After the time slot 6 has passed, the node 4 104 has data traffic of‘0’, and may be omitted because the node 4 104 is a leaf node.

That is, after the time slot 4 to the time slot 6 have passed in quarter2, all nodes perform data transmission once, and the data traffic ofeach of the node 3 103, the node 4 104, and the node 8 108, which areleaf nodes in the quarter 2, become ‘0’. Also, the data traffic of eachof the node 2 102 and the node 5 105 becomes ‘1’.

Referring to FIG. 7, the data traffic of each of the node 2 102 and node5 105 becomes ‘1’ in time slot 7, and the node 2 102 transmits data tothe parent node thereof through a transmission channel assigned theretodepending on the transmission schedule in the time slot 7.

After the time slot 7 has passed, the data traffic of the node 2 102becomes ‘0’.

Further, the node 5 105 transmits data to the parent node thereofthrough a transmission channel assigned thereto depending on thetransmission schedule in time slot 8.

After time slot 8 has passed, the node 2 102 has data traffic of ‘1’,and the node 5 105 has data traffic of 0, and then may be omittedbecause the node 5 105 is a leaf node.

Also, the node 2 102 transmits data to the parent node thereof throughthe transmission channel assigned thereto depending on the transmissionschedule in time slot 9.

After time slot 9 has passed, the node 2 102 has data traffic of ‘0’,and may be omitted because the node 2 102 is a leaf node.

That is, after the time slots 7 to 9 have passed in quarter 3, all nodesperform data transmission once, and the data traffic of all nodes exceptthe root node 101 becomes ‘0’, and thus the transmission procedure maybe completed without collisions or interference between nodes.

FIGS. 8 and 9 are diagrams illustrating a system using a dynamicscheduling method for guaranteeing QoS depending on network transmissiontraffic according to another embodiment of the present invention and adata transmission schedule based on the system.

Referring to FIG. 8, node 18 818, node 21 821, and node 22 822 are addedto the example of FIG. 1. A parent node of the node 18 818 is node 2802, a parent node of the node 21 821 is node 6 806, and a parent nodeof the node 22 822 is the node 21 821.

The numeral in each node illustrated in FIG. 8 indicates the ID of thecorresponding node, and the numeral on the left side of the nodeindicates a data traffic volume, which is the sum of the amount of datathat is received from descendant nodes and is to be transmitted to aroot node and the amount of data that is to be transmitted from thecorresponding node to the root node.

The larger the data traffic volume, the higher the priority for timeslot assignment that may be set in each quarter.

Here, when the priority for time slot assignment is set depending on thedata traffic volume, the priority that is assigned may become higher inthe sequence of node 2, node 3, node 5, node 6, node 4, node 8, node 21,node 7, node 9, node 18, and node 22.

Referring to the IEEE 802.15.4 standard when transmission channels areassigned to respective nodes, the total number of channels is 16, andthus channels ranging from #0 to #15 may be present.

Here, when the transmission channel is assigned to each node, atransmission channel having a channel number identical to the ID of aparent node of the corresponding node may be assigned. Also, when the IDof the parent node is equal to or greater than 16, which is the totalnumber of channels, the transmission channel may be replaced with achannel having a channel number corresponding to the remainder that isobtained when the ID of the parent node is divided by 16.

That is, channel #1 may be assigned as the transmission channel 802 a ofthe node 2 802, may be assigned as the transmission channel 803 a of thenode 3 803, and may be assigned as the transmission channel 804 a of thenode 4 804. Also, channel #2 may be assigned as the transmission channel805 a of the node 5 805, channel #3 may be assigned as the transmissionchannel 806 a of the node 6 806, channel #4 may be assigned as thetransmission channel 807 a of the node 7 807, and channel #5 may beassigned as the transmission channel 808 a of the node 8 808. Also,channel #8 may be assigned as the transmission channel 809 a of the node9 809, the channel #2 may be assigned as the transmission channel 818 aof the node 18 818, channel #6 may be assigned as the transmissionchannel 821 a of the node 21 821, and the channel #5 may be assigned asthe transmission channel 822 a of the node 22 822.

Referring to FIG. 9, when time slots are assigned in quarter 1 usingpriorities for time slot assignment and the assigned channelinformation, time slot 1 is assigned to the node 2 802, the node 6 806,the node 7 807, the node 8 808, and the node 22 822. Further, time slot2 is assigned to the node 3 803, the node 5 805, the node 9 809, and thenode 21 821, and time slot 3 is assigned to the node 4 804 and the node18 818.

Here, nodes higher than the node 8 808 and the node 22 822 are the node5 805 and the node 21 821, respectively. However, the total number ofchannels is 16, and there are channels from #0 to #15, and thus the samechannel, that is, channel #5, is assigned to the node 8 808 and the node22 822. Therefore, since the node 8 808 and the node 22 822 transmitdata through the same channel #5 in the same time slot #1, interferenceor a collision may occur. Therefore, there is a need to schedule datatransmission while avoiding interference.

FIG. 10 is a diagram illustrating an example in which the system using adynamic scheduling method for guaranteeing QoS depending on networktransmission traffic, illustrated in FIGS. 8 and 9, avoids interferenceand performs scheduling.

Referring to FIG. 10, the system using a dynamic scheduling method forguaranteeing QoS depending on network transmission traffic according tothe embodiment of the present invention may change time slots assignedto nodes between which interference or a collision occurs so as to avoidinterference when interference occurs between nodes upon scheduling datatransmission.

According to the schedule illustrated in FIG. 9, the node 8 and the node22 transmit data through the same channel #5 in the same time slot #1,and thus a problem may arise in that interference or a collision occurs.Therefore, the problem of a collision or interference may be avoided bychanging the time slot assigned to the node 22, which is one of nodes inwhich a collision occurs.

The node 22 uses the channel #5, and, in this case, the problem of acollision with the node 8 may occur in the time slot #1 and the problemof a collision with the node 5 may occur in the time slot #2, and thusthe problem of interference or a collision may be avoided by assigningthe time slot #3 to the node 22.

In this case, each quarter may include sufficient spare time slots so asto avoid the problem of interference or a collision.

The number of spare time slots included so as to avoid the problem ofinterference or a collision may be optimized for each quarter, and maythen differ for each quarter.

In a selective embodiment, when the node 8 and the node 22 cannotsuccessfully transmit data due to a collision or interference in an n-thslot frame at the time of transmitting data depending on the presetschedule, it may be determined that a schedule overlapping is present,and then retransmission may be prepared for. Here, retransmission may beactually performed through the channel #5 in the time slot #4, which isa spare time slot.

Here, the node 8 having higher priority for time slot assignmentattempts retransmission first, and a schedule for the node 22 havinglower priority for time slot assignment may be assigned to channel #5 intime slot #3 in quarter 1 in an (n+1)-th slot frame. Further, the node 8which has successfully completed retransmission may perform again a datatransmission schedule through channel #5 in time slot #1 in quarter 1 inthe (n+1)-th slot frame without changing the existing schedule.

In this way, when spare time slots are included in each quarter and acollision or interference occurs in data transmission, the assigned timeslot may be changed, and thus the problem of a collision or interferencethat may occur in data transmission may be effectively avoided andsolved.

FIG. 11 is a diagram illustrating another example in which the systemusing a dynamic scheduling method for guaranteeing QoS depending onnetwork transmission traffic, illustrated in FIGS. 8 and 9, avoidsinterference and performs scheduling.

Referring to FIG. 11, when interference occurs in the scheduling of datatransmission, the system using a dynamic scheduling method forguaranteeing QoS depending on network transmission traffic according tothe embodiment of the present invention may change any of transmissionchannels assigned to nodes between which interference or a collisionoccurs in order to avoid the interference.

According to the schedule illustrated in FIG. 9, node 8 and node 22transmit data through the same channel #5 in the same time slot #1, andthus a problem may arise in that interference or a collision occurs.Therefore, the problem of a collision or interference may be avoided bychanging the transmission channel assigned to the node 22, which is oneof nodes between which the collision occurs.

The node 22 uses the channel #5 in the time slot #1, and in this case,the problem of a collision with node 8 may occur in the time slot #1.Therefore, the problem of interference or a collision may be avoided byassigning channel #2, which is a transmission channel in whichcollisions with other nodes do not occur in the time slot #1, to thenode 22.

In this case, each quarter may include sufficient spare time slots so asto avoid the problem of interference or a collision.

The number of spare time slots included so as to avoid the problem ofinterference or a collision may be optimized for each quarter, and maythen differ for each quarter.

When a transmission channel is changed and assigned, a channel havingthe smallest channel number, among transmission channels in whichinterference or a collision does not occur, may be primarily assigned.

Here, when the transmission channel is changed, the channelcorresponding to the ID of the node in which interference or a collisionhas occurred, the channel corresponding to the ID of a parent node ofthe node in which interference or a collision has occurred, and thechannel corresponding to the ID of the corresponding node itself may beexcluded.

Also, in order to choose transmission channels to be excluded from thechange of transmission channels, information about channels used byrespective nodes to transmit data to parent nodes thereof may bereceived from neighboring nodes.

In this way, when spare time slots are included in each quarter and acollision or interference occurs in data transmission, the assignedtransmission channel may be changed, and thus the problem of a collisionor interference that may occur in data transmission may be effectivelyavoided and solved.

FIG. 12 is a diagram illustrating a method in which the system 1 using adynamic scheduling method for guaranteeing QoS depending on networktransmission traffic, illustrated in FIG. 1, sends an Enhanced Beacon(EB) message and Broadcast (BR) data.

Referring to FIG. 12, in the system 1 using a dynamic scheduling methodfor guaranteeing QoS depending on network transmission traffic,illustrated in FIG. 1, an Enhanced Beacon (EB) message containsimportant information for generating and controlling a network topologyand routing information. Further, the EB message is periodically sentfrom a parent node to a descendant node at beacon intervals. Whenmultiple nodes periodically send and receive beacon messages whilebooting in a large-scale wireless sensor network, a collision betweenpackets may occur, and a bottleneck phenomenon may be caused, thusconsequently not only resulting in a delay in the network join time ofthe corresponding node but also deteriorating network performance.

For this, as illustrated in FIG. 12, separately from quarters in whichdata is transmitted, a schedule for sending an EB message may be addedto a quarter EB interval.

Here, each node may establish a channel using its node ID, and may sendan EB message through the channel.

When there occurs a collision with an EB message which is sent from aneighboring node through the same channel, the EB message may be delayed(backed off) to a subsequent time slot, and may then be resent.

In this case, delay priority may vary depending on a hop count, a datatransmission success rate, a data traffic volume, the number of childnodes, or the like.

Further, the EB message contains a portion indicating whether there isdata to be transmitted in a quarter BR interval, and the data may bebroadcasted in the quarter BR interval subsequent to the quarter EBinterval if the portion indicates that there is the data to betransmitted.

Accordingly, neighboring nodes having received the EB message may decidewhether to receive the broadcast data, thus reducing energy consumptionand solving the problem of a broadcast storm by selectively using BRintervals.

FIG. 13 is an operation flowchart illustrating a dynamic schedulingmethod for guaranteeing QoS depending on network transmission trafficaccording to an embodiment of the present invention.

Referring to FIG. 13, the dynamic scheduling method for guaranteeing QoSdepending on network transmission traffic according to the embodiment ofthe present invention assigns communication channels based on the IDs ofparent nodes at step S1301.

Here, communication channels having channel numbers identical to the IDsof the parent nodes may be assigned.

When the total number of communication channels is set to N, acommunication channel having a channel number identical to the remainderthat is obtained by dividing each parent node ID by N may be assigned.

In particular, referring to the IEEE 802.15.4 standard, the total numberof channels is 16, and channels ranging from #0 to #15 may be present.In this case, a channel having a channel number identical to theremainder that is obtained by dividing the parent node ID by 16 may beassigned.

Further, the dynamic scheduling method for guaranteeing QoS depending onnetwork transmission traffic according to the embodiment of the presentinvention may set priorities for time slot assignment within eachquarter, based on a data traffic volume obtained by summing the amountof data that is received from descendant nodes and is to be transmittedto a root node and the amount of data that is to be transmitted from thecorresponding node itself to the root node at step S1303.

Here, the larger the data traffic volume, the higher the priority fortime slot assignment that may be set.

That is, the highest priority for time slot assignment may be set forthe node having the largest data traffic volume.

The total number of quarters may be identical to the largest datatraffic volume.

Next, the dynamic scheduling method for guaranteeing QoS depending onnetwork transmission traffic according to the embodiment of the presentinvention assigns time slots in each quarter at step S1305.

In this case, the time slots are sequentially assigned to nodes havingpriorities for time slot assignment in descending order of priority, andthe assignment of time slots is performed such that interference or acollision with previously assigned transmission channels does not occur.

All nodes are each assigned one time slot within one quarter, and thusthey may transmit data once within one quarter.

Next, the dynamic scheduling method for guaranteeing QoS depending onnetwork transmission traffic according to the embodiment of the presentinvention transmits data to the parent node of the corresponding node inthe assigned time slots at step S1307.

Further, the dynamic scheduling method for guaranteeing QoS depending onnetwork transmission traffic according to the embodiment of the presentinvention assigns communication channels for receiving an EB message atstep S1309.

Here, each communication channel for receiving an EB message may beassigned based on the ID of the corresponding node itself.

The communication channel for receiving an EB message may be assigned asa channel number identical to the ID of the corresponding node itself.

When the total number of communication channels is set to N, acommunication channel having a channel number identical to the remainderthat is obtained when the ID of the corresponding node is divided by Nmay be assigned.

Next, the dynamic scheduling method for guaranteeing QoS depending onnetwork transmission traffic according to the embodiment of the presentinvention receives an EB message using the assigned communicationchannel for receiving the EB message at step S1311.

Here, the reception of the EB message may be performed in a quarter EBinterval.

When a collision with a neighboring node occurs at the time of receivingan EB message, the EB message may be delayed (backed off) to asubsequent time slot, and may then be received again.

Further, the dynamic scheduling method for guaranteeing QoS depending onnetwork transmission traffic according to the embodiment of the presentinvention determines whether information indicating whether there isdata to be transmitted is contained in the EB message at step S1313.

If it is determined at step S1313 that the information indicating thatthere is data to be transmitted is contained in the EB message,broadcast data is received at step S1315.

If it is determined at step S1313 that information indicating that thereis data to be transmitted is not contained in the EB message, broadcastdata is not received.

Accordingly, a minimum number of time slots required in order totransmit and receive data may be assigned and used without interferenceor a delay, and thus a duty cycle may be minimized, with the result thatpower consumption may also be minimized.

Furthermore, neighboring nodes having received the EB messages maydecide whether to receive broadcast data, thus reducing energyconsumption and solving the problem of a broadcast storm by selectivelyusing BR intervals.

FIG. 14 is an operation flowchart illustrating an example of the timeslot assignment step 1305 illustrated in FIG. 13.

Referring to FIG. 14, in a procedure at time slot assignment step S1305,illustrated in FIG. 13, ‘n’, corresponding to the index of each timeslot, is set to ‘1’ at step S1401.

Further, in the procedure at time slot assignment step S1305 illustratedin FIG. 13, when a previously assigned transmission channel is used inan n-th time slot, whether interference or a collision occurs isdetermined at step S1403.

If it is determined at step S1403 that interference or a collision doesnot occur in the n-th time slot, the n-th time slot is assigned at stepS1405.

If it is determined at step S1403 that interference or a collisionoccurs in the n-th time slot, whether ‘n’ falls within a quarter boundcorresponding to a current quarter is determined at step S1407. In otherwords, whether the n-th time slot is the last time slot in the currentquarter is determined.

Here, in each quarter, spare time slots needed to change and assign atime slot when the problem of a collision or interference occurs may beincluded.

Also, the number of spare time slots to be included in each quarter maybe optimized and may differ for each quarter.

If it is determined at step S1407 that ‘n’ falls within the quarterbound corresponding to the current quarter, a subsequent time slot stillremains, and thus the value of the time slot index ‘n’ is increased by‘1’ at step S1409. Then, the process returns to step S1403 ofdetermining whether the problem of a collision or interference occurs.

If it is determined at step S1407 that ‘n’ does not fall within thequarter bound corresponding to the current quarter, the n-th time slotis the last time slot in the current quarter. In this case, regardlessof which time slot is assigned, it is impossible to avoid the occurrenceof a collision or interference with other nodes. Accordingly, thecommunication channel is changed at step S1411, and the process returnsto step S1401 of determining again whether a collision or interferenceoccurs from the first time slot.

When the communication channel is changed, a transmission channelcorresponding to the ID of the corresponding node, a transmissionchannel corresponding to the ID of a parent node of the correspondingnode, and a transmission channel corresponding to the ID of a node whichcauses a collision or interference with the corresponding node may beprimarily excluded.

Accordingly, either a time slot or a communication channel is changed inorder to solve the problem of a collision or interference that may occurin data transmission, so that all nodes may transmit data withoutcollisions in each quarter, thus removing a delay time and preventingdata loss.

Specific executions, described in the present invention, are onlyembodiments, and are not intended to limit the scope of the presentinvention using any methods. For the simplification of the presentspecification, a description of conventional electronic components,control systems, software, and other functional aspects of systems maybe omitted. Further, connections of lines between components shown inthe drawings or connecting elements therefor illustratively showfunctional connections and/or physical or circuit connections. In actualdevices, the connections may be represented by replaceable or additionalvarious functional connections, physical connections or circuitconnections. Further, unless a definite expression, such as “essential”or “importantly,” is specifically used in context, the correspondingcomponent may not be an essential component for the application of thepresent invention.

In accordance with the present invention, by means of the coloring-baseddynamic distributed scheduling method and the system using the method,collisions and interference may be removed when a large number ofmulti-hop nodes configured in a large-scale IoT environment desire totransmit data to a root node, thus enabling communication between nodesto be efficiently performed.

Further, by means of the coloring-based dynamic distributed schedulingmethod and the system using the method, a transmission delay time may bedecreased and a transmission success rate may be improved by dividingquarters according to the amount of network transmission traffic whilecollisions and interference, occurring in transmission, may be avoidedand data may be transmitted without overlapping by separating time andchannels based on coloring.

Therefore, the spirit of the present invention should not be defined bythe above-described embodiments, and it will be apparent that allmatters disclosed in the accompanying claims and equivalents thereof areincluded in the scope of the spirit of the present invention.

What is claimed is:
 1. A dynamic scheduling method for guaranteeingQuality of Service (QoS) depending on network transmission traffic,comprising: assigning communication channels to respective nodes basedon Identifications (IDs) of parent nodes corresponding to the respectivenodes; determining priorities for assignment of time slots to therespective nodes in each quarter based on data traffic volumescorresponding to the respective nodes, a frame length being divided intoa plurality of quarters, each quarter including multiple time slots; andassigning time slots to the respective nodes in each quarter dependingon the determined priorities for assignment of the time slots, whereinthe dynamic scheduling method further comprises: assigning communicationchannels to the respective nodes so as to receive an Enhanced Beacon(EB) message in a quarter assigned to the EB message, separate fromexisting quarters in which data is transmitted; and allowing each of thenodes to receive an EB message from a parent node corresponding theretothrough the assigned communication channel, wherein assigning the timeslots comprises sequentially determining, for a target node, whether acommunication collision occurs in multiple time slots from a first timeslot in a target quarter, and assigning an earliest time slot in which acommunication collision does not occur to the target node, and whereinthe dynamic scheduling method further comprises: when two or more targetnodes interfere with each other using an identical channel in anidentical time slot in an identical target quarter, changing andassigning one or more of communication channels and time slots that areassigned to the interfering target nodes.
 2. The dynamic schedulingmethod of claim 1, wherein assigning the time slots comprises assigningthe time slots such that a collision between neighboring communicationchannels does not occur by applying graph coloring to the communicationchannels.
 3. The dynamic scheduling method of claim 1, wherein: thetarget quarter comprises one or more spare time slots for avoidinginterference, and changing and assigning the one or more of thecommunication channels and the time slots comprises assigning differenttime slots to the interfering target nodes using the spare time slots.4. The dynamic scheduling method of claim 1, wherein changing andassigning the one or more of the communication channels and the timeslots comprises, when two or more target nodes interfere with each otherusing an identical channel in an identical time slot in an identicaltarget quarter, assigning different communication channels to theinterfering target nodes.
 5. The dynamic scheduling method of claim 4,wherein changing and assigning the one or more of the communicationchannels and the time slots comprises, when the different communicationchannels are assigned to the interfering target nodes, assigning thedifferent communication channels to the interfering target nodes usingcommunication channels other than existing communication channels of theinterfering target nodes and existing communication channels of parentnodes of the interfering target nodes.
 6. The dynamic scheduling methodof claim 1, further comprising: when information, indicating that thereis data to be transmitted in a quarter assigned for Broadcast (BR), isincluded in the EB message, receiving broadcast data corresponding tothe data to be transmitted in the quarter for BR.
 7. The dynamicscheduling method of claim 1, wherein determining the priorities forassignment of time slots comprises determining a priority for assignmentof time slots to a higher level as a data traffic volume correspondingto each node is larger.
 8. The dynamic scheduling method of claim 7,wherein assigning the time slots comprises assigning the time slots suchthat each node performs transmission once or less in each quarter.
 9. Asystem using a dynamic scheduling method for guaranteeing Quality ofService (QoS) depending on network transmission traffic, wherein thedynamic scheduling method is configured to: assigning communicationchannels to respective nodes based on Identifications (IDs) of parentnodes corresponding to the respective nodes, determining priorities forassignment of time slots to the respective nodes in each quarter basedon data traffic volumes corresponding to the respective nodes, a framelength being divided into a plurality of quarters, each quarterincluding multiple time slots, and assigning time slots to therespective nodes in each quarter depending on the determined prioritiesfor assignment of the time slots, wherein the dynamic scheduling methodis configured to: assigning communication channels to the respectivenodes so as to receive an Enhanced Beacon (EB) message in a quarterassigned to the EB message, separate from existing quarters in whichdata is transmitted; and allowing each of the nodes to receive an EBmessage from a parent node corresponding thereto through the assignedcommunication channel, wherein the time slots are assigned bysequentially determining, for a target node, whether a communicationcollision occurs in multiple time slots from a first time slot in atarget quarter, and by assigning an earliest time slot in which acommunication collision does not occur to the target node, and whereinthe dynamic scheduling method is configured to, when two or more targetnodes interfere with each other using an identical channel in anidentical time slot in an identical target quarter, change and assignone or more of communication channels and time slots that are assignedto the interfering target nodes.
 10. The system of claim 9, wherein thetime slots are assigned such that a collision between neighboringcommunication channels does not occur by applying graph coloring to thecommunication channels.
 11. The system of claim 9, wherein: the targetquarter comprises one or more spare time slots for avoidinginterference, and the dynamic scheduling method is configured to assigndifferent time slots to the interfering target nodes using the sparetime slots.
 12. The system of claim 9, wherein the dynamic schedulingmethod is configured to, when two or more target nodes interfere witheach other using an identical channel in an identical time slot in anidentical target quarter, assign different communication channels to theinterfering target nodes.
 13. The system of claim 12, wherein thedynamic scheduling method is configured to, when the differentcommunication channels are assigned to the interfering target nodes,assign the different communication channels to the interfering targetnodes using communication channels other than existing communicationchannels of the interfering target nodes and existing communicationchannels of parent nodes of the interfering target nodes.
 14. The systemof claim 9, wherein the dynamic scheduling method is configured to: wheninformation, indicating that there is data to be transmitted in aquarter assigned for Broadcast (BR), is included in the EB message,receive broadcast data corresponding to the data to be transmitted inthe quarter for BR.
 15. The system of claim 9, wherein the prioritiesfor assignment of time slots are determined such that a priority forassignment of time slots is determined to a higher level as a datatraffic volume corresponding to each node is larger.
 16. The system ofclaim 15, wherein the time slots are assigned such that each nodeperforms transmission once or less in each quarter.
 17. A dynamicscheduling method for guaranteeing Quality of Service (QoS) depending onnetwork transmission traffic, the method comprising: assigningcommunication channels to respective nodes based on Identifications(IDs) of parent nodes corresponding to the respective nodes; determiningpriorities for assignment of time slots to the respective nodes in eachquarter based on data traffic volumes corresponding to the respectivenodes, a frame length being divided into a plurality of quarters, eachquarter including multiple time slots; assigning time slots to therespective nodes in each quarter depending on the determined prioritiesfor assignment of the time slots; and when two or more target nodesinterfere with each other using an identical channel in an identicaltime slot in an identical target quarter, changing and assigning one ormore of communication channels and time slots that are assigned to theinterfering target nodes, wherein assigning the time slots comprisessequentially determining, for a target node, whether a communicationcollision occurs in multiple time slots from a first time slot in atarget quarter, and assigning an earliest time slot in which acommunication collision does not occur to the target node.